Antibacterial Activity of Papaya Leaf Extracts Against Pathogenic Bacteria

It was reported that the extracts of papaya leaves could inhibit the growth of Rhizopus stolonifer. Antibacterial activity of Carica papaya leaf extracts on pathogenic bacteria was observed in this study. Papaya leaves were extracted by using maceration method and three kinds of solvents: ethanol, ethyl acetate, and hexane. Papaya leaf extracts were tested against Bacillus stearothermophilus, Listeria monocytogenes, Pseudomonas sp., and Escherichia coli by agar diffusion method. The objectives of this study were to determine extract ability against pathogenic bacteria, to observe the influence of pH, NaCl, and heat on extracts ability, and to observe extract ability against B. stearothermophilus spores. The data showed that ethyl acetate extract could inhibit B. stearothermophilus, L. monocytogenes, Pseudomonas sp., and E. coli. The extract activity was influenced by pH, and it was more effective in low pH. The extract activity was influenced by NaCl against B. stearothermophillus and E. coli. However, it was not influenced by NaCl in bioassay against L. monocytogenes and Pseudomonas sp. The extract activity was influenced by heating process against all the bacteria tested. The extracts inhibited B. stearothermophilus spores as well. Papaya leaves are potential natural anti-bacteria, which might be used in certain kinds of food

Silicon nanoparticles and interstellar extinction

To examine a recently proposed hypothesis that silicon nanoparticles are the source of extended red emission (ERE) in the interstellar medium, we performed a detailed modeling of the mean Galactic extinction in the presence of silicon nanoparticles. For this goal we used the appropriate optical constants of nanosized Si, essentially different from those of bulk Si due to quantum confinement. It was found that a dust mixture of silicon nanoparticles, bare graphite grains, silicate core-organic refractory mantle grains and three-layer silicate-water ice-organic refractory grains works well in explaining the extinction and, in addition, results in the acceptable fractions of UV/visible photons absorbed by silicon nanoparticles: 0.071-0.081. Since these fractions barely agree with the fraction of UV/visible photons needed to excite the observed ERE, we conclude that the intrinsic photon conversion efficiency of the photoluminescence by silicon nanoparticles must be near 100%, if they are the source of the ERE.Comment: Latex2e, uses emulateapj.sty (included), multicol.sty, epsf.sty, 6 pages, 3 figures (8 Postscript files), accepted for publication in ApJ Letters, complete Postscript file is also available at http://physics.technion.ac.il/~zubko/eb.html#SNP

X-ray Halos and Large Grains in the Diffuse Interstellar Medium

Recent observations with dust detectors on board the interplanetary spacecraft Ulysses and Galileo have recorded a substantial flux of large interstellar grains with radii between 0.25 and 2.0 mu entering the solar system from the local interstellar cloud. The most commonly used interstellar grain size distribution is characterized by a a^-3.5 power law in grain radii a, and extends to a maximum grain radius of 0.25 mu. The extension of the interstellar grain size distribution to such large radii will have a major effect on the median grain size, and on the amount of mass needed to be tied up in dust for a given visual optical depth. It is therefore important to investigate whether this population of larger dust particles prevails in the general interstellar medium, or if it is merely a local phenomenon. The presence of large interstellar grains can be mainly inferred from their effect on the intensity and radial profiles of scattering halos around X-ray sources. In this paper we examine the grain size distribution that gives rise to the X-ray halo around Nova Cygni 1992. The results of our study confirm the need to extend the interstellar grain size distribution in the direction of this source to and possibly beyond 2.0 mu. The model that gives the best fit to the halo data is characterized by: (1) a grain size distribution that follows an a^-3.5 power law up to 0.50 mu, followed by an a^-4.0 extension from 0.50 mu to 2.0 mu; and (2) silicate and graphite (carbon) dust-to-gas mass ratios of 0.0044 and 0.0022, respectively, consistent with solar abundances constraints. Additional observations of X-ray halos probing other spatial directions are badly needed to test the general validity of this result.Comment: 17 pages, incl. 1 figure, accepted for publ. by ApJ Letter

Viscoelasticity near the gel-point: a molecular dynamics study

We report on extensive molecular dynamics simulations on systems of soft spheres of functionality f, i.e. particles that are capable of bonding irreversibly with a maximum of f other particles. These bonds are randomly distributed throughout the system and imposed with probability p. At a critical concentration of bonds, p_c approximately equal to 0.2488 for f=6, a gel is formed and the shear viscosity \eta diverges according to \eta ~ (p_c-p)^{-s}. We find s is approximately 0.7 in agreement with some experiments and with a recent theoretical prediction based on Rouse dynamics of phantom chains. The diffusion constant decreases as the gel point is approached but does not display a well-defined power law.Comment: 4 pages, 4 figure

Entwicklung von Phytophthora-resistentem Zuchtmaterial für den ökologischen Landbau

Die Ansprüche des ökologischen Landbaus an Kartoffelsorten unterscheiden sich zum Teil erheblich von denen des konventionellen Anbaus. Dies ist bedingt durch den alternativen Pflanzenschutz mit mechanischer Unkrautbekämpfung sowie durch eine in der Regel geringere Stickstoffversorgung der Pflanzen. Darum benötigt der ökologische Landbau spezielle Sorten, die neben den vom Verbraucher gewünschten Qualitätsmerkmalen auch eine hohe Widerstandsfähigkeit gegenüber Krankheiten und Schädlingen besitzen, durch schnelle Jugendentwicklung das Unkrautwachstum unterdrücken und eine hohe Nährstoffeffizienz aufweisen. Um neue Zuchtstämme zu schaffen, in denen die im Biolandbau gewünschten Eigenschaften kombiniert vorliegen, etablierte das seit 2012 im „Bundesprogramm Ökologischer Landbau und andere Formen nachhaltiger Landwirtschaft“ geförderte Projekt „Entwicklung von Phytophthora-resistentem Zuchtmaterial für den ökologischen Landbau“ ein Zuchtprogramm speziell für den ökologischen Kartoffelanbau. Für die Züchtung auf geringe Anfälligkeit gegenüber der Kraut- und Knollenfäule, die durch den Oomyceten Phytophthora infestans hervorgerufen wird, wurde auf resistente Kartoffelklone aus der Vorzüchtung des Julius-Kühn Institutes zurückgegriffen. Die untersuchten Zuchtstämme und Vergleichssorten wurden parallel in einem Beobachtungsanbau hinsichtlich weiterer agronomischer und qualitativer Eigenschaften wie Ertragsleistung, Wuchsform, Stärkegehalt, Speise- und Veredelungseignung und Abreifeverhalten untersucht. Weitere Resistenzen sowie gewünschte Qualitätsmerkmale wurden aus modernen Hochleistungssorten deutscher Züchtungsunternehmen und historischen Sorten der IPK Genbank während des Projektverlaufs ins Zuchtmaterial eingebracht. Neben der Evaluierung der Prüfglieder hinsichtlich der Resistenzeigenschaften wurden zur Erweiterung des Basiszuchtmaterials zahlreiche Kreuzungen durchgeführt. Hierbei wurden die Kreuzungseltern gezielt aus den im Projekt geprüften Sorten und Zuchtstämmen ausgewählt. Für die Bewertung und die Selektion der Klone wurde ein partizipativer Züchtungsansatz gewählt und dafür drei ökologisch wirtschaftende, landwirtschaftliche Betriebe ins Projekt eingebunden. Die Betriebsleiter wurden intensiv geschult und führten die Bewertung der Klone und die Selektion der Knollen in enger Zusammenarbeit mit den wissenschaftlichen Mitarbeitern der Institute durch. Ein solches Modell ist bislang in der der deutschen Kartoffelzüchtung einzigartig. Wissenschaftlich begleitet wurden die Züchtungsarbeiten durch eine phänotypische und genotypische Charakterisierung des Ausgangsmaterials und der Zuchtklone. Ziel hierbei war es, Grundlagen für eine molekulare Selektion KF-resistenter Nachkommen zu schaffen. Hierzu wurden an einem Prüfgliedsortiment Assoziationsstudien mit DArT- und SNP-Markern durchgeführt und ausgewertet. Im Projekt wurden am IPK erstmalig zwei Sortimente umfassend genetisch mittels zwei verschiedener Markersysteme zu charakterisiert. Mit den erzielten Ergebnisse konnten Duplikatgruppen innerhalb der Genbankakzessionen aufgedeckt sowie Unstimmigkeiten erkannt und bereinigt werden. Damit wurde das Genbankmanagement verbessert und nutzerorientiert gestaltet. Somit hat das Projekt eine nachhaltigere und intensivere Nutzung pflanzengenetischer Ressourcen ermöglicht. Dadurch ist es Züchtern wie auch Forschungsinstitutionen zukünftig möglich, zielgerichteter auf genetische Ressourcen der Kartoffel zuzugreifen und diese in die eigenen Zuchtprogramme und Forschungsprojekte einzubringen

Quantum Smoluchowski equation: Escape from a metastable state

We develop a quantum Smoluchowski equation in terms of a true probability distribution function to describe quantum Brownian motion in configuration space in large friction limit at arbitrary temperature and derive the rate of barrier crossing and tunneling within an unified scheme. The present treatment is independent of path integral formalism and is based on canonical quantization procedure.Comment: 10 pages, To appear in the Proceedings of Statphys - Kolkata I

Developmental Testing of Habitability and Human Factors Tools and Methods During Neemo 15

Currently, no established methods exist to collect real-time human factors and habitability data while crewmembers are living aboard the International Space Station (ISS), traveling aboard other space vehicles, or living in remote habitats. Currently, human factors and habitability data regarding space vehicles and habitats are acquired at the end of missions during postflight crew debriefs. These debriefs occur weeks or often longer after events have occurred, which forces a significant reliance on incomplete human memory, which is imperfect. Without a means to collect real-time data, small issues may have a cumulative effect and continue to cause crew frustration and inefficiencies. Without timely and appropriate reporting methodologies, issues may be repeated or lost. TOOL DEVELOPMENT AND EVALUATION: As part of a directed research project (DRP) aiming to develop and validate tools and methods for collecting near real-time human factors and habitability data, a preliminary set of tools and methods was developed. These tools and methods were evaluated during the NASA Extreme Environments Mission Operations (NEEMO) 15 mission in October 2011. Two versions of a software tool were used to collect observational data from NEEMO crewmembers that also used targeted strategies for using video cameras to collect observations. Space habitability observation reporting tool (SHORT) was created based on a tool previously developed by NASA to capture human factors and habitability issues during spaceflight. SHORT uses a web-based interface that allows users to enter a text description of any observations they wish to report and assign a priority level if changes are needed. In addition to the web-based format, a mobile Apple (iOS) format was implemented, referred to as iSHORT. iSHORT allows users to provide text, audio, photograph, and video data to report observations. iSHORT can be deployed on an iPod Touch, iPhone, or iPad; for NEEMO 15, the app was provided on an iPad2

Interfacial layering in a three-component polymer system

We study theoretically the temporal evolution and the spatial structure of the interface between two polymer melts involving three different species (A, A* and B). The first melt is composed of two different polymer species A and A* which are fairly indifferent to one another (Flory parameter chi_AA* ~ 0). The second melt is made of a pure polymer B which is strongly attracted to species A (chi_AB 0). We then show that, due to these contradictory tendencies, interesting properties arise during the evolution of the interface after the melts are put into contact: as diffusion proceeds, the interface structures into several adjacent "compartments", or layers, of differing chemical compositions, and in addition, the central mixing layer grows in a very asymmetric fashion. Such unusual behaviour might lead to interesting mechanical properties, and demonstrates on a specific case the potential richness of multi-component polymer interfaces (as compared to conventional two-component interfaces) for various applications.Comment: Revised version, to appear in Macromolecule